MathsYears 2–3Addition & Subtraction

Use inverse to check

Recognise and use the inverse relationship between addition and subtraction to check calculations and solve missing number problems

What you'll learn

  1. 1

    Adding and subtracting undo each other. You can use one to check the other.

  2. 2

    If 25 + 13 = 38, then 38 − 13 must be 25. Going forwards and back brings you home.

  3. 3

    If 40 + 15 = 55, what is 55 − 15?

  4. 4

    Checking with the inverse catches mistakes without doing the sum twice the same way.

  5. 5

    Jo works out 62 − 28 = 44. Check: 44 + 28 = 72, not 62. So it is wrong. The right answer is 34, because 34 + 28 = 62.

  6. 6

    How would you check that 71 − 36 = 35?

  7. 7

    Why not just repeat the subtraction to check?

Practise Use inverse to check with Whizlo

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